The present invention relates to a production method for an implant.
In implants, it can be advantageous if, for example, individual screw holes or openings can be selectively opened. This is particularly important in hip joint sockets, since abrasion particles from the joint socket can pass through unused screw holes into the area between implant and bone. However, in osteosynthesis plates, it can also be advantageous to selectively close individual screw openings or to be able to remove certain areas of the implant.
It is therefore proposed in FR 2826865 to produce hip joint sockets in which the screw holes are closed by covers that are secured on the outside of the joint socket by individual weld points. If one of the screw holes is needed, the cover can be removed by breaking these weld points.
U.S. Pat. No. 5,782,929 discloses a hip joint socket made of titanium, in which the screw openings are closed by titanium plugs that have been sintered with the joint socket. The plugs are produced separately from the hip joint socket and are only later fitted into the openings. The plugs are connected to the socket by sintering for several hours in an oven at ca. 1200° C.
A disadvantage of the two methods described is that the production of such joint sockets involves several steps and, as a result, is correspondingly complex. In addition, the strength of the connection of the covers or plugs to the joint socket can be different depending on the opening.
WO 2010/023447 describes a prosthesis made of carbon-fiber-reinforced polyether ether ketone (CFR-PEEK). In one embodiment, the screw openings can be closed by pieces that can be broken out. During production, a predetermined break line is in this case created in the area of the openings by means of targeted reduction of the material thickness. The prosthesis can be produced from one piece by machining or can also be produced by injection molding.
It is known from EP 0 701 420 that hip joint sockets with removable covers that can be broken out can be produced by drilling cylindrical blind holes on the inner face of the socket. The blind holes are formed in such a way that a material thickness of below 0.65 mm remains between the outer face of the joint socket and the end of the hole. In this way, the cover over the blind hole can be broken out when so required.
FR 2 838 329 describes a hip joint socket having screw openings closed by covers that are connected materially to the hip joint socket. The covers are bounded by an area of reduced material thickness, which allows the covers to be easily broken out. Toward the interior of the joint socket, the covers have additional projections, into which further plugs can be fitted.
It is likewise known from U.S. Pat. No. 5,370,702 that removable covers over screw openings can be produced by reduced material thickness. The covers disclosed in this patent have, in the direction of the interior of a hip joint socket, spike-like projections that can be gripped by a suitable tool and that make the covers easier to break out.
EP 1 338 256 describes a hip joint socket with screw openings that can be punched out. The material thickness of the hip joint socket is reduced in the area of these openings in order to make them easier to punch out. This document also describes tools for punching out the screw openings. The area with reduced material thickness can additionally have a circular notch in order to additionally reduce the punching-out force needed for removal.
The stated covers have the principal disadvantage that problems are caused by their production by machining and by the necessary small material thicknesses, since these material thicknesses often lie within the fault tolerance of customary machines in the case of multiple clamping. Moreover, on account of the required precision, their production is laborious and expensive.